Fuse and fuse element supports for use therein



g- 1969 B. T. M ALLISTER ET AL 3,460,085

FUSE AND FUSE ELEMENT SUPPORTS FOR USE THEREIN Filed Sept. 21, 1967 [Ill/Ill I FIG. 5 5O FIG.2

INVENTORS Byron T. McAllister 8 Wilson C. Good WWW ATTORNEY United States Patent 3,460,085 FUSE AND FUSE ELEMENT SUPPORTS FOR USE THEREIN Byron T. McAllister, Pittsburgh, and Wilson C. Good, Level Green, Tratford, Pa., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Sept. 21, 1967, Ser. No. 669,433 Int. Cl. H01h 85/36 US. Cl. 337-190 17 Claims ABSTRACT OF THE DISCLOSURE A fuse has two spirally wound fuse elements each composed of a notched or perforated strip extending parallel to each other through the fuse tube and being spaced from each other at the ends by spacer bars composed of insulating material and clamped to the two fuse elements near the ends thereof. Because of the low self-supporting strength of the thin, spirally wound elements, support is added at the center of the fuse tube to prevent sagging of the elements and obtain correct interrupting characteristics. Endsupport is provided to prevent rolling of the element spacer plates or bars under the sand load. The end support includes a formed wire and is self-supporting after being snapped into place, exerting spring tension against the fuse elements.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to fuses having parallel spirally wound fuse elements disposed in a fuse tube filled with an arc extingushing material such as sand. Supports are provided for the fuse elements to prevent sagging of the fuse elements and to prevent rolling of the element spacer plates or spacer bars under sand load.

DESCRIPTION OF THE PRIOR ART Somewhat similar disc-shaped members composed of conductive material located between the ends of the fuse tube and the inner surfaces of the conductive ferrules are shown and described in the copending patent application of Frank L. Cameron for Fuses, Ser. No. 487,408, filed Sept. 15, 1965, and assigned to the assignee of the instant invention. The disc-shaped members of the copending application have central openings therein and have tabs extending from the disc toward the center of the fuse tube. However, in the embodiments of that copending application which employ two parallel fuse elements, each element extends around its own tab, the two elements passing around tabs on opposite sides of the Opening. In the instant application, the tabs of our invention are wider or longer, and two parallel fuse elements have their ends passing around the same tab, the other tab being used to anchor an end support member for the fuse elements. We provide new and unique means for clamping two spiral fuse elements in spaced position with respect to each other at the ends of a fuse tube, provide a novel aforementioned end support placed inside the ferrule "ice which clamps each fuse element against its tab electrical contact member, which is self-supporting when snapped in place, and which prevents the sand load from dragging down the ends of the fuse elements, and we provide a new and novel support for a spirally wound fuse element or elements at substantially the axial center of the fuse tube to prevent sagging, and in effect distributing the sand weight over two sections of the element, preventing the spacing between turns in the upper half of the fuse from being elongated and the spacing between turns in the lower half from being compressed.

SUMMARY OF THE INVENTION The fuse has two spirally wound fuse elements spaced apart by spacer bars clamped near their ends, the elements extending in parallel paths through a fuse tube, each of the elements comprising a notched or perforated strip, with cross arm supporting means extending across the fuse tube at substantially the center of each element over which one turn of each fuse element laps, and secured to the inner wall of the fuse tube, maintaining the correct spacing of the turns of the elements. Additionally, end fuse element support elements are provided, clamping each fuse element against its tab electrical contact at its junction therewith and preventing the rolling or sagging of the spacer bars under sand load, which would stretch the fuse element beyond permissible limits and destroy the proper turn spacing thereof, the end support being self-supporting when once snapped in place and exerting spring tension against the fuse elements and spring tension against the spacer bars.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a longitudinal section through the fuse of our invention, showing the two fuse elements employed therein, the spacer bars, the center support and one of the end supports;

FIG. 2 is a side elevational view of the center support for the spiral fuse elements;

FIGS. 3A and 3B are side views of an end support for the fuse elements taken at two angles degrees With respect to each other;

FIG. 4 is a sectional view through the fuse in a transverse plane, along the line IV-IV of FIG. 5, showing the end support in position therein;

FIG. 5 is a fragmentary sectional view through the fuse, showing the center support from a different angular perspective and showing an additional view of a fuse element end support and its manner of supporting a spacer bar; and

FIG. 6 is an internal view in perspective of half of the fuse of our invention showing the two fuse elements,

the center support, a spacer bar and an end support snapped into position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Particular reference is made to FIG. 1 where a fuse generally designated 10 is shown as having a fuse tube 11 composed of electrically insulating material, with ferrules 12 and 13 mounted on the ends thereof respectively and having threaded terminal studs 14 and 15 respectively.

Two spirally Wound fuse elements 21 and 22 extend in parallel paths through the fuse tube, the elements being shown as notched strips, but it will be understood that the elements could be perforated strips, or could have other configurations, each arranged to provide a number of burn-through points as by a number of areas of relatively small cross-section along the length of the fuse element, or other suitable means. At the left hand end of the fuse, FIG. 1, fuse elements 21 and 22 are seen to be clamped between two spacer bars which may be of glass polyester riveted together by rivets 24, 25 and 26, one of the bars being shown at 23. The right-hand ends of the two fuse elements are clamped between two spacer bars 27 and 28, FIG. 5, riveted together by rivets 29, 30 and 31, FIG. 1. At the left-hand end of the fuse, FIG. 1, it is seen that a disc-like electrical contact and terminal member 33 is disposed between the end of the fuse tube and the inside surface of the ferrule, the contact member having a central opening, not shown in FIG. 1, and having two tabs at the sides of the opening and extending from the disc portion toward the center of the fuse tube, these two tabs being shown at 34 and 35. Contact member 33 composed of electrically conductive material, makes electrical contact with the ferrule, and the two fuse elements 21 and 22 are seen making electrical contact with the aforementioned tab 34.

Dis-posed within the fuse tube substantially at the axial center thereof, FIG. 1, is a center fuse element support member composed of insulating material generally designated 37, shown in side elevation in FIG. 2, having an offcenter arm portion 38 extending thereacross and having an 'arcuate portion 39 which closely fits the inside surface of the aforementioned fuse tube 11. The arcuate portion 39 has one end 40 thereof terminating adjacent the offcenter arm portion, and has the other end 41 thereof terminating in a manner to leave a gap of slightly over 90 in the arcu-ate portion, although it will be understood that the length of the angular gap is not critical.

Particular reference is made to FIG. 5, a fragmentary section through the fuse in a plane at 90 with respect to the plane of FIG. 1 and showing the center support member generally designated 37 from a different view. It is seen that the fuse element 22 has one turn which is substantially the center turn thereof lying across the offcenter arm portion 38 of the center-support member generally designated 37, the off-center arm portion 38 not being visible in FIG. but being back of the end 40 of the arcuate portion of the fuse element support member. At the right-hand end of FIG. 5 the fuse element 22 is seen to be clamped between the aforementioned spacer bars 27 and 28 and thence to pass around the lower tab 43 of the disc-like supporting and contact member 44 composed of electrically conductive material, the member 44 being disposed between the right-hand end of the fuse tube 11 and the ferrule 13, member 44 having an additional tab 45, with an opening in the member 44 between the tabs, this opening not being visible in FIG. 5 but being shown at 47 in FIGS. 4 and 6. It is seen in FIG. 5 that the end of the fuse element 22 lies closely adjacent the aforementioned tab 43 and after passing along the tab has a portion 49 thereof lying between member 44 and the inner end surface of the ferrule, and has the end portion 50 thereof bent around the outside wall of the fuse tube and extending along a portion of the length thereof adjacent the end of the fuse tube, this end portion 50 of the fuse element being firmly clamped between the inner surface of the ferrule 13 and the outer wall surface of the fuse tube 11.

In FIG. 5 a generally U-shaped end support member generally designated 52 is seen having an elongated portion thereof pressing against the tab 45 and a portion thereof pressing against the portion of the fuse element adjacent the tab 43 and holding this portion of the fuse element firmly against the tab while also exerting spring tension against the spacer bars 27 and 28 to prevent their falling down toward the ferrule as they would if unsupported when sand was poured into the fuse tube.

Particular reference is made to FIG. 3A where the end support member generally designated 52 is further seen to be generally U-shaped and to have a first bent portion 53 bent at substantially at one end thereof and to have an additional bent portion 54 at the other end thereof, the portion 54 being bent at an angle less than 90 and in a plane different from that in which the bend 53 occurs.

Particular reference is made now to FIG. 4, a section taken along the line IVIV of FIG. 5. Both the fuse elements 21 and 22 are seen in FIG. 4, both passing around the aforementioned tab 43 with portions 48 and 49 of the fuse elements respectively passing back of the disc portion of member 44 and thence being bent around and adjacent the end of the fuse tube and being clamped between the outer wall surface of the fuse tube and the inner surface of the ferrule. End support member generally designated 52 is seen in place in FIG. 4 with one extended anm portion thereof lying along the inner surface of the tab 45 with the bend 54 preventing slippage of the support member, and the other elongated portion with 90 bent portion 53 lying against the two fuse elements 21 and 22 and forcing them tightly against the tab 43. It will be understood that end support element 52 while in place exerts spring tension upon the fuse elements and upon the tab, and also tends to force spacer bars 27 and 28, FIG. 5, to the left against the weight of sand poured into the fuse tube. Particular reference is made to FIG. 6, a perspective view of half of the length of the fuse of FIG. 1, showing the fuse elements 21 and 22, the central fuse element support 37 with the off-center arm 38 across which the turns of the fuse elements loop and are supported thereby, the two spacer bars 27, 28, rivets 29, 30 and 31, and contact member 44 having a central aperture 47 therein with tabs 45 and 43 at the sides thereof, and end support member 52 which is disclosed shown clipped in place, exerting spring tension which not only holds the two fuse elements 21 and 22 firmly against the tab 43, but tending to force the supporting or clamping bars 27 and 28 to the left, or toward the axial center of the fuse tube, FIG. 6, and prevent the supporting orspacer bars 27 and 28 from being moved into the space between tabs as a result of the weight of sand on the bars as the tube is filled with sand from the other end, thereby stretching the turns of the fuse elements beyond permissible limits and destroying the desired spacing between the turns.

Summarizing, a fuse is provided having a substantially central fuse element support which prevents sagging of the fuse elements and thereby insures correct interrupting characteristics. Further, end supports are provided at the ends of the fuse elements to prevent rolling of the element spacer bars or elongation or compression of the turns of the fuse element under sand load. The fuse element center support is preferably cemented to the inside of the fuse tube and supports the fuse elements at their centers, in effect distributing the sand weight over two sections of each element, preventing the nearly complete opening of the element turns at the top and the nearly complete closing of the turns at the bottom. The central fuse element support may be composed of or cut from fiber sheet having sufiicient rigidity, and may be designed to be self-supporting until cemented to the inside wall of the fuse tube. The end support element is placed inside the terminal of the fuse and clamps each fuse element against the tab contact at its junction with the clamping bars, preventing the rolling or sagging of the clamping bars under sand load, which would stretch the fuse elements beyond permissible limits. The end support is a wire form and is self-supporting after being snapped into place.

Whereas we have illustrated our invention by a fuse having two spirally wound fuse elements extending in parallel paths, it will be understood that the invention includes a fuse having only one spirally wound element.

The foregoing written description and the drawings are illustrative and exemplary only and are not to be interpreted in a limiting sense.

We claim as our invention:

1. A fuse including a fuse tube, at least one spirally wound fuse element extending through the fuse tube, ferrules at the end of the fuse tube making electrical connection with the ends of the fuse element, a pair of means secured to the ferrules for clamping the ends of the fuse element respectively against axial and radial movement in the fuse tube, said fuse tube being substantially filled with sand, and supporting means in the fuse tube substantially centrally located along the axis of the fuse tube for engaging at least one turn of the spirally wound fuse element and thereby preventing dislocation of the fuse element while the fuse tube is being filled with sand.

2. A fuse according to claim 1 in which the supporting means is an arcuate shaped member composed of insulating material and having an off-center arm extending thereacross, the adjacent turn of the fuse element resting on said arm, said support member being secured to the inside wall of the fuse tube.

3. A fuse according to claim 1 in which the means for clamping the ends of the fuse element against axial and radial movement each includes two adjacent plates, and means disposed at the end of the fuse tube and exerting spring tension against the supporting plates whereby the plates are secured to the ferrules and prevented from rolling under the sand load and being moved toward the bottom of the fuse tube thereby stretching the fuse element beyond permissible limits and disturbing the spacing of the turns of the fuse element.

4. A fuse according to claim 3 including in addition a disc-like member composed of conductive material disposed between the end of the fuse tube and the adjacent surface of the ferrule, the disc-like member having an opening therein and having a pair of tabs on the sides of the opening, said tabs extending toward the axial center of the fuse tube, said fuse element normally lying adjacent one of said tabs, said means exerting spring tension against the supporting plates being generally U- shaped with one elongated portion lying adjacent the inner surface of one tab and the other elongated portion lying adjacent the fuse element and the other tab and exerting spring tension on the supporting plate and on the fuse element.

5. A fuse according to claim 1 in which the supporting means substantially centrally located along the axis of the fuse tube for engaging at least one turn of the spirally wound fuse element is secured to the inside of the fuse tube and supports the fuse element at its approximate center thereby in effect distributing the sand weight over two sections of the fuse element and preventing the nearly complete opening of the turns of the fuse element at the top of the fuse and the nearly complete closing of the turns of the fuse element at the bottom of the fuse as a result of filling the fuse tube with sand.

6. A fuse according to claim 1 including in addition a second spirall wound fuse element within the fuse tube, the second fuse element extending parallel to the first-named fuse element and being spaced therefrom, said supporting means also engaging at least one turn of the second spirally wound fuse element.

7. A fuse according to claim 6 in which one of the pair of means secured to the ferrules for clamping the ends of the fuse element includes first and second spacer bars at one end of the fuse tube, means clamping the first and second spacer bars to the adjacent ends of the two fuse elements thereby spacing said fuse element and said second fuse element from each other, in which the other one of the pair of means secured to the ferrules for clamping the end of the fuse element includes third and fourth spacer bars at the other end of the fuse tube, and means clamping the third and fourth spacer bars to the adjacent ends of the two fuse elements thereby spacing the fuse element and said second fuse element from each other.

8. A fuse according to claim 6 in which the supporting means is composed of insulating material and is secured to the inside of the fuse tube, said supporting means in cluding an arcuate portion fitting the inside curvature of the wall of the fuse tube, and an arm portion extending across the fuse tube, the adjacent turns of both fuse elements resting on the arm portion.

9. A fuse according to claim 7 wherein the means for clamping the fuse element against axial and radial movement in the fuse tube includes first and second disc-like members composed of conductive mateiral disposed between the ends of the fuse tube and the ferrules, each of the disc-like members having an opening therein with tabs on each side of the opening, the adjacent ends of the two fuse elements lying adjacent the same one of said tabs, and a generally U-shaped spring-like end support member having one elongated portion pressing against one of the tabs and the other elongated portion pressing against the two fuse elements and pressing the fuse elements against the other tab with spring tension.

10. A fuse according to claim 9 in which the supporting means for a turn of the fuse element is composed of insulating material and includes an arcuate portion curved to fit the inside curvature of the fuse tube and an arm portion extending transversely across the fuse tube, adjacent turns of the two fuse elements resting on said arm portion and being supported thereby.

11. A fuse element support for use in a fuse having a cylindrical fuse tube adapted to be filled with sand and having at least one spirally wound fuse element extending therethrough, the fuse support element being composed of insulating material and having an arcuate portion curved to fit the curvature of the inside wall of the fuse tube and adapted to be secured to the inside wall of the fuse tube, the support element having an arm portion adapted to extend across the fuse tube, one turn of the fuse element resting on said arm portion and being supported thereby whereby the sand weight is in effect distributed over two sections of the fuse element preventing the nearly complete opening of the turns of the fuse element in that portion of the fuse tube which constitutes the top thereof during the sand filling process and preventing the closing of the turns of the fuse element in that portion of the fuse tube which constitutes the bottom thereof during the sand filling process.

12. A fuse element support for use in a fuse having at least one spirally wound fuse element extending through a fuse tube adapted to be filled with sand and having an end member composed of conductive material disposed between the end of the fuse tube and the adjacent ferrule, the end member having an opening therein with tabs extending on both sides of the opening toward the axial center of the fuse tube, the fuse element support being a generally U-shaped spring member having one elongated portion disposed adjacent one of the tabs and the other elongated portion disposed adjacent the fuse element and the other tab and pressing the fuse element against the last-named tab, thereby holding the end of the fuse element in place under the sand load and preventing the sand load from stretching the fuse element beyond permissible limits.

13. A fuse according to claim 1 in which the fuse element is a notched strip.

14. A fuse according to claim 1 in which the fuse element is a perforated strip.

15. A fuse according to claim 7 in which both the first-named spirally wound fuse element and the second spirally wound fuse element are notched strips.

7 8 16. A fuse according to claim 7 in which both the 2,337,937 12/1943 Serfling et a1 337-231 first-named fuse element and the second fuse element 1,392,917 10/1921 Conant 337-236 are spirally Wound perforated strips.

17. A fuse element support according to claim 12 in FOREIGN TE which the fuse element support member is additionally 807,347 1/1959 Great Bntamcharacterized as having bent end portions at each end 0 thereof, said bent end portions assisting in keeping the BERNARD GHJHEANY Pnmary Exammer fuse element support in position within the tabs. H. B. GILSON, Assistant Examiner References Cited 10 US. Cl. X.R. UNITED STATES PATENTS 295 368,765 8/1887 Hammer 337---290 2,113,155 4/1938 Kiefer 337-276 X 

